Sigismund III Vasa

Sigismund III Vasa (20 June 1566-30 April 1632) was King of Poland and Grand Duke of Lithuania from 18 September 1587 to 19 April 1632, succeeding Anna Jagiellon and Stephen Bathory and preceding Wladyslaw IV Vasa, as well as King of Sweden from 17 November 1592 to 24 July 1599, succeeding John III and preceding Charles IX.

Biography
Sigismund was born in Gripsholm Castle, Sweden on 20 June 1566, the son of the future King John III of Sweden and Catherine Jagellonica of Poland. His parents were at the time being held as prisoners of King Eric XIV of Sweden, and his family was released in 1567; in 1568, Eric XIV was deposed and succeeded by John. As the grandson of King Sigismund I the Old of Poland, he was elected King of Poland-Lithuania in 1587; he was also Crown Prince of Sweden due to his father's title of King. Maximilian III, Archduke of Austria, a rival claimant to the Polish throne, invaded Poland to press his claim, but he failed to capture the Polish capital of Krakow and was forced to surrender after being defeated at Byczyna on 24 January 1588. In 1589, Sigismund released Maximilian after he renounced his claim to the Polish throne.

King of Sweden
In 1592, King John of Sweden died, and the Sejm agreed to allow for Sigismund to inherit the Swedish throne, while the Swedes agreed to his accession after he agreed that Lutheranism was to remain the state religion. He appointed his uncle Duke Charles as regent in Sweden while he ruled from Krakow, but his uncle later led a rebellion against Sigismund in 1598, claiming that he would defend Protestantism from the Catholic Sigismund. At Stangebro, Sigismund's army was defeated, and Charles had his Swedish loyalists executed before seizing power himself. The result of this was the Polish-Swedish Wars, and the union of Poland and Sweden would never be recovered.

Reign in Poland
Sigismund would come to consider Poland as a tool to eventually regain the throne of Sweden, and he allied himself with the Habsburgs and the Counter-Reformation forces. He constantly had to deal with the rebellious szlachta nobility in Poland, as well as external threats such as the Grand Duchy of Moscow, the Ottoman Empire, and Sweden. Commonwealth forces were shuffled between wars with the Swedes in the north, the Russians to the east, and the Turks to the south, but he took advantage of the Time of Troubles in Russia to make territorial acquisitions, pacifying his own rebellious nobles. In 1608, he crushed the semi-legal "Zebrzydowski Rebellion", but the szlachta retained their dominance in the Polish political system.

During the Thirty Years' War, Sigismund sought to intervene on the Catholic side, but the Sejm prevented him from doing so. He ultimately decided against risking his country's power and prestige in Eastern Europe, as he had made the Commonwealth a dominant power in Eastern and Central Europe during his reign. He died of a stroke in 1632 at the age of 65 in Warsaw.